+1 for the almost keyboard only method. Rock on!!!
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pcapademicJan 19 '10 at 23:24

@EricJLN While a little clumsy, you can do keyboard-only by pressing CTRL+A to select all, then using the keys to navigate to the file you want to keep, and pressing CTRL+SPACE.
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ZurahnJan 20 '10 at 0:13

To select a file in a folder, you can type the filename whilst the folder has focus. Windows will select the file that matches what you have typed up to that point. Then Ctrl+A, Ctrl+Space, Delete. (Or use above script)